Transistors, such as metal oxide semiconductor field-effect transistors (MOSFETs), are the core building block of the vast majority of semiconductor devices. Some semiconductor devices, such as high performance processor devices, can include millions of transistors. For such devices, decreasing transistor size, and thus increasing transistor density, has traditionally been a high priority in the semiconductor manufacturing industry.
A FinFET is a type of transistor that can be fabricated using very small scale processes. FIG. 1 is a simplified perspective view of a FinFET 10, which is formed on a semiconductor wafer substrate 12. A FinFET is named for its use of one or more fins 14, which are formed from the semiconductor material of the substrate 12. As shown in FIG. 1, each fin 14 extends between a source region 16 and a drain region 18 of the FinFET 10. The FinFET 10 also includes a gate structure 20 that is formed over and across the fins 14. The surface area of the fins 14 in contact with the gate structure 20 determines the effective channel of the FinFET 10.